Someone had asked how you can have one Nest Thermostat control another. I had a similar problem (for some reason I have two thermostats which run two different condensers that heat and cool the same room.
I could not create a routine in Nest or Google Nest to solve the problem, so instead I used Smart Things, linked both into my account and set up five routines.
1. When control thermostat status is 'cooling' set slave thermostat to 'cooling'.
2. 10 seconds after control's status is 'cooling' set slave temp to 60.
3. When control status is 'idle' set slave to 'off'.
4. When control status is 'heating' set slave to 'heat'.
5 10 seconds after control status is 'heating' set temp to 80.
There might be an easier way, but that's what I came up with. I had to set the temperatures to set a few seconds after turning on the slave, as the temperature did not set from the off status. Good luck and happy hunting!
Moderator edit: Subject updated for clarity and findability.
